1. Field of the Invention
This invention relates in general to industrial dust collectors and, in particular, to an improved bottom loading filter bag assembly for the baghouse of an industrial dust collector. More specifically, but without restriction to the particular description shown, this invention relates to a snap band provided at the open end of a filter bag having an internal support cage, the band and cage allowing the bag to be quickly mounted and sealed within the tube sheet of a baghouse from beneath the tube sheet.
2. Discussion of the Prior Art
Demand from various industries for effective environmental control systems has recently been greater than heretofore because of the advent of increasingly stringent environmental regulations. One area of particular concern has been air quality control. In a wide variety of industries dealing with the processing of bulk materials such as cement, chemicals, fertilizers, food grains, paper and minerals, dust collectors well known in the art have typically been employed to remove airborne particulate matter from the processing environment.
These dust collectors commonly include a hopper and an upper housing having a baghouse. A tube sheet is provided in the upper housing to support a number of cylindrical filter bags. The filter bags typically include an internal wire cage or stiff ribbing for structural support. The tube sheet effectively divides the upper housing into two distinct regions. These two regions include a filter bag region or baghouse situated below the tube sheet and a clean air chamber above the tube sheet. In this known configuration, the filter bags are suspended downwardly from the tube sheet. The bottom end of each bag is closed while the top end is open. A circular hole for each filter bag is provided in the tube sheet so that the open end of the bag can be placed in communication with the clean air chamber. The hopper of the dust collector typically contains an inlet connected to an internal baffle while the clean air chamber includes an outlet in communication with an exhaust or draft fan.
In operation, dust laden air is removed from the processing environment by an air duct connected to the hopper inlet. This dirty air is distributed within the upper housing by the internal baffle, which reduces air velocity and disperses the air uniformly throughout the housing. Heavier dust particles are separated from the airstream and fall into the hopper. Lighter, airborne particles are collected on the outside surface of the filter bags while the air is drawn through the bag fabric and upward inside the bag, past the tube sheet, and then into the clean air chamber. From there it is continually drawn through ducts to be induced draft fan. At this point, the filtered air is either discharged to the atmosphere or returned to the processing environment. Periodically, the bags are cleaned by a jet of high pressure air emitted through blow tubes placed horizontally in the clean air chamber above the open top of a row of bags. The downward flowing air jet causes accumulated dust to be dislodged from the outside surface of the bags. This dust then falls into the hopper. All the dust and particulate matter collected in the hopper is removed therefrom by an airlock or a screw conveyor and airlock combined.
The above-described dust collector is typically placed on the exterior of the facilities that contain the processing environment. In this type of installation, the outlet and inlet of the dust collector would have potentially long air ducts leading to and from the facility or building containing the processing environment. When the dust collector is so positioned without any overhead obstructions, the 5 to 8 foot filter bags can easily be installed and replaced through access panels provided in the top of the dust collector.
In some applications, however, the dust collector is better positioned within the interior of the building or structure containing the processing environment. Overhead obstructions are often encountered in these installations, thus making it desirable to be able to install and replace the long filter bags from beneath the tube sheet rather than through access panels in the top of the baghouse. To accommodate the installation and replacement of these bottom loading filter bags, the baghouse is provided with a side access panel positioned below the tube sheet.
Prior bottom loading filter bags include a wire mesh cage that extends from the bottom of the filter bag to its open end. A collar is placed around the open end of the wire cage. The material forming the filter bag is folded over the collar and tucked into the interior of the wire cage. To mount this type of bottom loading filter bag, the tube sheet is provided with a downwardly projected collar welded around the hole provided in the tube sheet. These known bottom loading filter bags are mounted by sliding the cage collar over the tube sheet collar and then securing the assembly by use of a hose clamp. In this arrangement, the filter material of the bag is sandwiched between the two collars.
These prior bottom loading filter bags are limited in that the portion of the filter material folded over into the interior of the supporting wire cage will crimp thereby creating small folds around the interior of the filter bag opening. The small folds create paths between the cage and tube sheet collars that allow dirt or dust laden air to enter directly into the interior of the filter bag and then into the clean air chamber. This leakage can occur even when the hose clamp is fully tightened. The baghouse of an industrial dust collector could typically contain over a hundred filter bags. The leakage occurring at one filter bag is thus increased by the total of bags contained in the baghouse. In addition, the use of a hose clamp, needing to be tightened manually for each individual filter bag, results in an excessive amount of time for installation and replacement of the filter bags.
Since dust collectors are increasingly required to capture virtually every particle of finer and finer dusts in a variety of environments, the above-discussed prior art filter bag assemblies are becoming outmoded.